Heat exchanger assembly having a common fluid box

ABSTRACT

A plurality of heat exchanger units are joined together by a connecting member in an end to end relation. A fluid box is formed between the units by the walls of the connecting member and the tube sheets of the joined units. The fluid box serves as a passageway to conduct the heat exchange fluid between heat exchanger units. A tie-bar connected to the tube sheets of the individual heat exchanger units assists in containing the bending stresses exerted on the tube sheets by the pressure of the exchange fluid.

United States Patent [191 Hagnauer May 22, 1973 HEAT EXCHANGER ASSEMBLYHAVTNG A COMMON FLUID BOX [76] Inventor: Waldo W. Hagnauer, 910 KeithAvenue, Waukegan, 111. 60085 [22] Filed: Apr. 16, 1970 [21] Appl. No.:29,065

[51] int. C1. ..F28f 9/02 [58] Field of Search ..165/140, 143, 144,165/145,158,176

[56] References Cited UNITED STATES PATENTS 3,393,731 7/1968 Friedman etal ..165/176 X 2,196,683 4/1940 Pickstone ..165/82 1,813,234 7/1931 Dodd..165/176 X 2,956,787 10/1960 Raub ..165/82 2,995,343 8/1961 Gardner eta1 ..165/143 X FOREIGN PATENTS OR APPLICATIONS 640,680 7/1950 GreatBritain ..165/143 952,965 3/1964 Great Britain...... ....l65/158 67,1901/1951 Netherlands ..165/158 Primary Examiner-William F. ODea AssistantExaminer-William C. Anderson Attorney-Petherbridge, ONeill and Lindgren[57] ABSTRACT A plurality of heat exchanger units are joined together bya connecting member in an end to end relation. A fluid box is formedbetween the units by the walls of the connectingmember and the tubesheets of the joined units. The fluid box serves as a passageway toconduct the heat exchange fluid between heat exchanger units. A tie-barconnected to the tube sheets of the individual heat exchanger unitsassists in containing the bending stresses exerted on the tube sheets bythe pressure of the exchange fluid.

10 Claims, 8 Drawing Figures PATENTEU HAY 22 5 SHEET 1 OF 4 RUEINVENTOR.

HAGNAUR ATTORNEYS.

PATENTEU M122 I975 FIG?) SHEET 3 BF 4 INVENTOR. WALDO HAGNAURPATENTEUHAYZZIQYS 3,734,176

SHEET U U? 4 FIG.5-

FIG?

HEAT EXCHANGER ASSEMELY HAVING A COMMON FLUID BOX BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to heatexchangers and more particularly to means for coupling a pair of heatexchangers through a fluid chamber which is common to both the heatexchangers.

Although heat exchanger assemblies may be used for various purposesincluding those for cooling, for convenience, the present invention willbe discussed in con nection with heat exchanger assemblies used forheating that provide a high heat exchange capacity with high fluidpressure.

2. The Prior Art In heat exchangers of the type to which this inventionrelates, there is usually provided a shell or housing within which isdisposed a bundle of elongated tubular members over which a fluidheating medium is passed. The tube bundle is supported or connected atat least one end by a flat plate partition structure or tube sheet,which divides the exchanger into two compartments. One of thecompartments is employed to direct a fluid through the tubes, while theother compartment is employed to permit a flow of warmer medium in goodheat exchange relation with the outer surfaces of the tubes withattendant heating of the fluid within the tubes. Heat exchangers of thistype are usually supplied with such fluids and operate at substantiallyhigh temperatures and pressures. In most installations such as a steamplant, a plurality of heat exchanger units is required for feed waterheating purposes. In high pressure boiler feedwater heaters for a steamturbine plant, for example, it is common practice to circulate the feedwater through the tubes and to extract steam from a turbine stage overthe tubes of a plurality of heat exchanger units, generally two or moreexchangers connected externally and arranged in series. In one form ofsuch heat exchangers, the feedwater enters and leaves the tubes viafluid boxes or headers located at each end of the tubes. In another formof heat exchanger unit, the tubes are arranged in U-shaped banks and theinlet and outlet ends of the tubes are joined to a common tube sheet.The fluid boxes for the inlet or outlet of the feedwater are arrangedside by side on the end face of the tube sheet remote from the tubes andare joined to the tube sheet. The fluid boxes may be formed by welding ahousing in the form of a solid forging to the tube sheet and dividingthe space within the housing into two separate fluid boxes by means of adividing wall.

The pressures at which the feedwater and steam are circulated, throughthe heat exchanger require that the tube sheet be able to withstand veryhigh pressures. In a modern steam plant, the highly stressed tube sheetmay require a thickness of 12 to 18 inches in order to withstandpressures as high as several thousand pounds per square inch betweenopposite sides of the tube sheets because of the high pressure fluidwithin the box. The fluid boxes, to withstand such pressures, must be ofa special strong design such as a spherical or hemisphericalconfiguration. Because of the thickness of the tube sheet and thespecial designs required for the fluid boxes, these heat exchangercomponents are costly to fabricate and the art is continually seekingways to simplify the design of the fluid boxes and reduce the thicknessof the tube sheets.

A primary object of the present invention is to provide a heat exchangerassembly wherein the means for providing heat exchange of fluids issimplified.

Another object of this invention is to provide a heat exchange apparatusfor heating fluids in applications requiring two or more separate heatexchangers wherein the number of fluid boxes and attendant equipment,such as external interconnecting piping, is reduced.

A further object of the invention is to provide a heat exchanger inwhich the thickness of the tube sheet is reduced and which may bemanufactured at much less cost.

The various novel details of construction and the advantages inherent inthe heat exchanger assembly of the present invention are pointed out indetail in conjunction with the following descriptions of typicalembodiments of the invention,

SUMMARY OF THE INVENTION In view of the foregoing it is contemplated bythe present invention to provide a heat exchanger assembly including aplurality of heat exchange units of which each unit has a housing closedby a formed end and an open end closed by a tube sheet. A tube bundlecomprised of a plurality of tubes is disposed in each of the housingswith the ends of the tubes being secured to the tube sheet. The heatexchanger units are joined together in an end-to-end relation with aconnecting member of which the walls and the spaced-apart tube sheets ofthe heat exchange units form a fluid box which serves as a passageway toconduct heat exchange fluid between the heat exchanger units.

The common fluid box interposed between the units of the heat exchangerassembly of the present invention eliminates the need for the pluralityof specially designed costly fluid boxes or closures, ordinarilyemployed in the art in the fabrication of such heat exchangerassemblies. This reduces the initial construction cost and thesubsequent interconnecting external piping between single exchangers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinalcross-sectional view through one embodiment of a heat exchanger assemblyhaving a common fluid box interposed between the heat exchange units inaccordance with the present invention.

FIG. 2 is a cross-sectional view taken generally along the line 2-2'ofFIG. I.

FIG. 2A is a cross-sectional view similar to FIG. 2,

showing a modified embodiment of the tie bar within the heat exchanger.

FIG. 3 is a longitudinal cross-sectional view through a secondembodiment of a heat exchanger assembly constructed in accordance withthe present invention.

FIG. 4 is a cross-sectional view taken generally along the line 4-4 ofFIG. 3.

FIG. 5 is a partial cross-sectional view of a tube sheet and a portionof the tie-bar illustrating the tie-bar encased within a covering to actas a heat transfer retardant. I

FIG. 6 is a partial cross-sectional view of a tube sheet and a portionof the tie-bar illustrating a tubular tie-bar functioning as a cascadevent between opposite heat exchanger units as well as aforce-containment device.

FIG. 7 is a partial cross-sectional view of a tube sheet and a portionof the tie-bar illustrating a tie-bar wherein the thickness thereof isvaried according to the structure of the connecting member.

' Referring to FIGS. 1 and 2 of the drawing the reference numeralgenerally designates an embodiment of a heat exchanger assemblyaccording to this invention. The heat exchanger assembly 10 consists oftwo heat exchanger units 11 and 12 which are joined together in a tandemor end-to-end relationship by a lowcost, high strength in tensioncylindrical coupling or connecting member 13, which is joined to theouter faces 15 and 16 of the tube sheets 17 and 18 of the individualheat exchanger units 11 and 12 by welding or other suitable attachmentmeans.

Each of the heat exchange units 11 and 12 includes an elongated,cylindrical housing or shell 20 and 21 respectively, the open ends ofwhich are closed with the plate-like tube sheets 17 and 18, which aresealingly fixed to the ends of walls 23, 24 of the housings as bywelding. The shells 20 and 21 and the inner walls 25, 26 of the tubesheets 17 and 18 form individual spaces 28, 29. Inlet openings 30, 31 inthe upper walls of respective shells 20 and 21 communicate the spaces28, 29 with a source of heat exchange medium.

Outlet openings 33 and 34 are provided in the lower walls of shells 20and 21 to permit the exhaust of the heat exchange fluid from spaces 28,29 afterthe heat exchange fluid has undergone heat exchange.

The alined, spaced outer walls 15, 16 of the tube sheets 17 and 18 andthe walls of the connecting member 13 form a common fluid distributionbox 35 between the heat exchangers 11 and 12. The fluid box 35 providesa passageway for conducting heat exchange fluid from the tubes of oneheat exchange unit to the tubes of the other heat exchange unit. Apartition structure 36 is provided and disposed within the fluid box 35in abutting relation withv a partition plate 37 attached to the upperportion of the outer wall 15 of the tube sheet, and partition 38attached to the upper wall of the connecting member 13 to jointly formtherewith a box or chamber 40 so that chamber 40 is in communicationwith the upper portion of tube sheet 17. Similarly, a

partition structure 43 is provided and disposed within the fluid box 35in abutting relation with partition 45 attached to the lower portion ofthe outer wall 16 of the tube sheet 18 and partition plate 46 attachedto the lower wall of the cylindrical connecting member 13 to jointlyform therewith a chamber 48 so that chamber 48 is in communication withthe lower portion of the tube sheet 18. Inlet conduit 51 attached to thelower wall of the coupling member 13 connects chamber 48 to a suitablesource of heat exchange fluid through fluid inlet port 52 in the lowerwall of coupling member 13.

Outlet conduit 54 in the upper wall of coupling member 13 permitsexhaust of the heat exchange fluid that collects in chamber 40 throughfluid outlet port 55 in the upper wall of coupling member 13 as willhereinafter be described.

Within the spaces 28 and 29 of shells 20 and 21, respectively, aredisposed tube bundles 57 and 58 comprising a plurality of tubes 59 and60. Each of the tube bundles consists of a plurality of various radius Usection tubes 61 and 62 with continuing straight portions extendingsubstantially parallel to each other and the longitudinal axis of theshells 20 and 21. The opposite ends 63, 64 of the tubes 59 and theopposite ends 65, 66 of the tubes are secured in their respective tubesheets 17 and 18 in any suitable manner as by swaging, welding or thelike. The opposite ends 63, 64 of the tubes 59 are secured to the tubesheet 17 so that tube end 63 communicates with fluid outlet chamber 40and tube end 64 communicates with fluid distribution box 35. Theopposite ends 65, 66 of the tubes 60 are secured in tube sheet 18 sothat the tube ends 65 communicates with common fluid box 35 and tubeends 66 communicates with fluid inlet chamber 48.

Accordingly, as thus far described, a first heat exchange fluid isadmitted to the heat exchange assembly 10 through inlet 51 where itpasses to chamber 48 and then through the tube ends 66 of tubes 60secured to the lower portion of tube sheet 18 disposed in heat exchangeunit 12 of heat exchanger assembly 10.

The fluid traverses heat exchange tubes 60 and is then directed into thecommon fluid box 35. From the fluid box 35 the first heat exchange fluidis passed to the tubes 59 disposed in heat exchanger unit 11 of the heatexchanger assembly 10, which communicate with fluid box 35 through thetube ends 64 secured to the lower portion of the tube sheet 17. Thefirst heat exchange fluid is exhausted from tubes 59 into the chamber 40through the tube ends 63 secured in the upper portion of the tube sheet17. The exhausted fluid then leaves the chamber 40 and the heat assembly10 through outlet conduit 54. Concomitantly therewith, as a second fluidis admitted into the chambers 28 and 29 of the individual heat exchangerunits of the heat exchanger assembly 10 through the inlet conduits 30and 31 and flows around the outer surfaces of tubes 59 and 60, heatexchange between the fluid flowing in the tubes and the fluid flowingthrough the spaces 28 and 29 is obtained.

Preferably as shown in FIG. 1, there is provided in the fluid box 35 atleast one longitudinally extending tie-bar 70 which is secured, as bywelding at its opposite ends to the outer walls 15, 16 of the tubesheets 17 and 18. The tie-bar 70 extends perpendicular to the tubesheets 17 and 18 and forms therewith an H-shaped assembly when viewed incross-section. The H-frame assembly formed by the tube sheets 17 and 18and the tie-bar 70 produces an extremely rigid structure which bycontainment of forces minimizes the diaphragmatic bending effect actingon the tube sheets by the high pressure exchange fluid within the fluidbox 35. The minimization of the stress forces acting on the tube sheetsreduces the strength requirements for the tube sheets and permits thethickness of the tube sheets to be substantially reduced. The reductionof the thickness of the tube sheets accounts for a substantial savingsin the fabrication costs of the heat exchanger assembly. Because of athinner tube sheet, the heat exchanger can accept more rapid changes inoperating conditions with less harmful affect on the device as a whole,particularly with reference to temperature changes between thethin-walled tubes and the heavy tube sheets.

The entire fluid box design, the tie bar, tube sheet diameter andthickness, number of tubes, ligament spac ing resulting from tubespacing, and other such parameters are computer calculated to arrive atan optimum design for the condition imposed.

Since the tie-bar 70 is exposed to fluid flow conditions on all sides,whereas the connecting member 13 is only exposed to fluid contact on theinternal wall surfaces thereof, the temperature response of the tie-bar70 to the fluid in the fluid box 35 may not always be coequal to that ofthe connecting member 13. The temperature sensitivity of the tie-bar 70may be adjusted by any suitable means. For example, to equalize theexpansion and contraction response of the tie-bar 70 and the walls ofthe connecting member 13 to the fluid in the fluid box 35, the thicknessof the tie-bar 70 may be increased to compensate for the difference inarea exposed to the fluid. To further compensate for the difference inexposure area or as an alternative to the use of a tie-bar of varyingthicknesses (70"), the tie-bar 70 may be encased in a sheath or sleeve(70A), or a suitable heat insulating material to permit equalizedexpansion and contraction with fluid temperature change.

Although the tie-bar 70 as shown in FIG. ll is of uniform cross-section,in the event that tube sheets of unlike size or cross-section areemployed in a heat exchanger assembly, it is understood to be within thepurview and scope of the present invention that tie-bars of variouscross-section, as for example tie-bars having a conical, oval, tubular,or other cross-section may be employed when required. FIG. 2Aillustrates one such embodiment wherein the tie bar 70a is shown to bein form of a tubular member, which may thereby serve the additionalfunction of a cascade vent (7013) between the opposed heat exchangers.

To permit access to the tubes 59, 60 for inspection, repair and cleaningof the tubes, the fluid box 35 is provided with a conventional manway ormanhole door 71. Partitions 36 and 43 may be in the form of removableplates to permit access for cleaning and repair of the tube ends incommunication with the chambers 40 and 48. For example, partition platecovers 36 and 43 may be fastened to partition plates 37, 38 and 45, 46respectively, by suitable bolts, welding or other means for removal notshown.

In FIGS. 3 and 4 there is shown a modified fluid box of the presentinvention. Since the only difference between this embodiment and theembodiment shown in FIGS. 1 and 2 lies in the fluid box, the heatexchanger units being identical, parts of the embodiment shown in FIGS.3 and 4 corresponding to like components of the heat exchanger shown inFIGS. 1 and 2 shall be designated by the same reference numbers.

In FIGS. 3 and 4, the fluid box 35 interposed between the heat exchangerunits 11 and 12 is divided into chamber 75, by centrally disposedforce-containing horizontal partition plate 76 which is welded'orotherwise secured to the outer walls 15, 16 of tube sheets 17, 18 andthe walls of the coupling member 13 and into chambers 78 and 79 byvertically extending partition plate 80, which is centrally disposed influid box 35 and is welded or otherwise secured to the bottom wall ofpartition plate 76 and the bottom wall of the coupling member 13.

The partition plates 76 and 80 serve the multiple purpose of dividingthe fluid box 33 into chambers 75, 78, 79 as well as reinforcing thetube sheets 17 and 18 so that the tube sheets are sufficiently able towithstand the bending forces imposed thereon by the pressure of fluidsflowing into the fluid box 35 in much the same manner as the tie-bar 70shown in the embodiment of the present invention illustrated in FIGS. 1and 2.

Inlet conduit 81 attached to the lower wall of coupling member 13communicates chamber 79 with a suitable source of a first heat exchangefluid through inlet port 82. Outlet conduit 83 permits exhaust of theheat exchange fluid that collects in chamber 78 through fluid outletport 84. Chamber provides a passageway for conducting a heat exchangefluid between the tubes of the individual heat exchange units.

In operation, a first exchange fluid is admitted to the heat exchangerassembly 10 through inlet conduit 81 where it passes into chamber 79 andthen through tube ends 66 of tubes 60. The fluid traverses tubes 60 andis then directed into chamber 75 and then into the tube ends 63 of tubes59. The fluid is passed from tubes 59 through the tube ends 64 intochamber 78 from which the fluid is exhausted from the heat exchangerassembly through outlet conduit 83. A second fluid is passed through theunits 11 and 12 in the same manner as described for the heat exchangerassembly illustrated in FIGS. 1 and 2, so that heat exchange between thefirst and second fluids is caused to occur.

To permit access to the fluid box for repair and maintenance of the boxand the heat exchanger tubes, manway 86 is provided which is sealed byremovable manway cover 87 and provides access to chamber 75. Fromchamber 75 access to chambers 78 and 79 is provided through manways 88and 89 which are sealed by removable partition plate covers 91 and 92.

The manway cover 87 and the partition plate covers 88 and 89 are held inplace by clamps 93, 94 and 95 respectively. By means of nuts 96, 97 and98 threaded on bolts connected to the covers and bearing against theclamps 93, 94 and 95, the manway cover 87 and partition plate covers 91and 92 are seated in fluid-tight engagement with the manways 86, 88 and89. To insure a fluid-tight seal the covers 87, 91 and 92 may beprovided with gaskets designated by the numeral 100.

From the foregoing it should be readily apparent that the presentinvention provides a heat exchanger assembly which is relatively simpleand less costly to fabricate and which is capable of easy access forinspection and repair.

Although two embodiments of the invention have been illustrated anddescribed in detail, it is to be ex pressly understood that theinvention is not limited thereto. Various changes can be made in thearrangement of parts without departing from the spirit and scope of theinvention as the same will now be understood by those skilled in theart.

What is claimed is:

l. A heat exchanger assembly comprising in combination,

at least a first and a second heat exchanger unit in series flow,

each of the heat exchanger units being comprised of a housing closed atboth ends,

at least one of the housing ends of each exchanger being closed by atube sheet,

a cavity defined by each tube sheet and the walls of each housing,

a plurality of tubes disposed in each cavity,

the opposite ends of said tubes being secured to said tube sheets,

first inlet and outlet means in communication with said plurality oftubes disposed in each cavity for the delivery and exhaust of a firstheat exchange fluid flowing in series,

a connecting member joining the heat exchanger tube sheets serially inan end to end relation for series flow of said first heat exchangefluid,

a fluid chamber formed between said heat exchanger units by the walls ofthe connecting member and the opposed tube sheets of the first andsecond heat exchanger units, the fluid chamber serving as a conduit forthe passage of said first heat exchange fluid between said units,

second inlet means in communication with said cavities of said first andsecond heat exchanger units for delivery of a second heat exchange fluidto the heat exchanger assembly and a second outlet means incommunication with said cavities of said first and second heat exchangerunits to provide an exhaust for the second heat exchange fluid from theheat exchanger assembly, and

means positioned within said fluid chamber and secured to each of saidtube sheets to form a rigid structural member minimizing bending of saidtube sheets resulting from pressure differentials acting across therespective tube sheets.

2. The assembly of claim 1, wherein the tubes secured to the tube sheetare U-shaped.

3. The assembly of claim 1 wherein a single fluidtight scalable manwayis provided in the fluid box for access to the tubes of opposed heatexchanger units.

4. The assembly of claim 1 wherein the common connecting fluid chamberof said first and second exchangers in series flow is partitioned intochambers for the inlet and exhaust of said first heat exchange fluid topass said first heat exchange fluid sequentially between said first andsecond heat exchanger units.

5. The apparatus of claim 1 wherein said means positioned within saidfluid chamber and secured to each of said tube sheets to form a rigidstructural member minimizing bending of said tube sheets resulting frompressure differential forms a partition within said fluid chamber topass a second heat exchange fluid from said first heat exchanger unit tosaid second heat exchanger unit.

6. The apparatus of claim 1 wherein said means positioned within saidfluid chamber and secured to each of said tube sheets to form a rigidstructural member minimizing bending of said tube sheets resulting frompressure differential comprises a tie-bar secured at its opposite endsto the opposed tube sheets of said first and second heat exchanger unitto minimize the diaphragmatic bending effect acting thereon due to thehigh pressure heat exchange fluid.

7. The assembly of claim 6 wherein one tie-bar is secured perpendicularto the tube sheets to form an H- frame assembly with said opposed tubesheets.

8. The assembly of claim 6 wherein said tie-bar is encased within acovering to act as a heat transfer retardant.

9. The assembly of claim 6 wherein said tie bar is tubular thereby tofunction as a cascade vent between opposite heat exchanger units as wellas functioning as a force-containment device.

10. The assembly of claim 6 wherein the thickness of said tie-bar isvaried according to the construction of the connecting member.

1. A heat exchanger assembly comprising in combination, at least a firstand a second heat exchanger unit in series flow, each of the heatexchanger units being comprised of a housing closed at both ends, atleast one of the housing ends of each exchanger being closed by a tubesheet, a cavity defined by each tube sheet and the walls of eachhousing, a plurality of tubes disposed in each cavity, the opposite endsof said tubes being secured to said tube sheets, first inlet and outletmeans in communication with said plurality of tubes disposed in eachcavity for the delivery and exhaust of a first heat exchange fluidflowing in series, a connecting member joining the heat exchanger tubesheets serially in an end to end relation for series flow of said firstheat exchange fluid, a fluid chamber formed between said heat exchangerunits by the walls of the connecting member and the opposed tube sheetsof the first and second heat exchanger units, the fluid chamber servingas a conduit for the passage of said first heat exchange fluid betweensaid units, second inlet means in communication with said cavities ofsaid first and second heat exchanger units for delivery of a second heatexchange fluid to the heat exchanger assembly and a second outlet meansin communication with said cavities of said first and second heatexchanger units to provide an exhaust for the second heat exchange fluidfrom the heat exchanger assembly, and means positioned within said fluidchamber and secured to each of said tube sheets to form a rigidstructural member minimizing bending of said tube sheets resulting frompressure differentials acting across the respective tube sheets.
 2. Theassembly of claim 1, wherein the tubes secured to the tube sheet areU-shaped.
 3. The assembly of claim 1 wherein a single fluid-tightsealable manway is provided in the fluid box for access to the tubes ofopposed heat exchanger units.
 4. The assembly of claim 1 wherein thecommon connecting fluid chamber of said first and second exchangers inseries flow is partitioned into chambers for the inlet and exhaust ofsaid first heat exchange fluid to pass said first heat exchange fluidsequentially between said first and second heat exchanger units.
 5. Theapparatus of claim 1 wherein said means positioned within said fluidchamber and secured to each of said tube sheets to form a rigidstructural member minimizing bending of said tube sheets resulting frompressure differential forms a partition within said fluid chamber topass a second heat exchange fluid from said first heat exchanger unit tosaid second heat exchanger unit.
 6. The apparatus of claim 1 whereinsaid means positioned within said fluid chamber and secured to each ofsaid tube sheets to form a rigid structural member minimizing bending ofsaid tube sheets resulting from pressure differential comprises atie-bar secured at its opposite ends to the opposed tube sheets of saidfirst and second heat exchanger unit to minimize the diaphragmaticbending effect acting thereon due to the high pressure heat exchangefluid.
 7. The assembly of claim 6 wherein one tie-bar is securedperpendicular to the tube sheets to form an H-frame assembly with saidopposed tube sheets.
 8. The assembly of claim 6 wherein said tie-bar isencased within a covering to act as a heat transfer retardant.
 9. Theassembly of claim 6 wherein said tie bar is tubular thereby to functionas a cascade vent betweEn opposite heat exchanger units as well asfunctioning as a force-containment device.
 10. The assembly of claim 6wherein the thickness of said tie-bar is varied according to theconstruction of the connecting member.